A Preliminary Study of I-Gel:A New Supraglottic Airway Device

Summary This preliminary study on I-gel TM (Intersurgical Ltd, Wokingham,U K) was conducted on 50 consecutive patients ofASA physical status I-III ,to determine the ease of insertion, time to achieve effective airway ,oropharyngeal seal pressure and airway stability on head and neck movement. After premedication with midazolam and fentanyl, induction was done with propofol and I-gel was inserted according to manufacturer’s instruction. An effective airway was confirmed by bilateral chest movement, square wave on capnograph and SpO 2 >95%. The success rate at first attempt was 90% with a median insertion time of 11 sec (range 8-45sec). Five patients (10%) needed second attempt while none needed 3 rd attempt. The manipulation needed to achieve effective airway were increasing the depth of insertion of I-gel in 4 (8%) cases , jaw thrust or chin lift in2(4%) cases.Oropharyngeal seal pressure was 20 cm of H 2 O (16-40 cm of H 2 O). Gastric tube placement was done in 50% of the cases; it was easy and successful in all the cases. No significant adverse event was noted in any of the patient in perioperative period. Our initial experience showed that I-gel is a simple, easy to use supraglottic airway device with a high success rate at first time insertion.


Introduction
I-gel TM (IntersurgicalLtd, Wokingham, U.K.) is a new supraglottic airway device with anatomically designed, non inflatable mask, which is soft, gel like and transparent,made ofthermoplastic elastomer 1 .The soft, non inflatable cuff fits snugly onto the perilaryngeal framework and its tip lies in the proximalopening of the oesophagus, isolating the oropharyngeal opening from the laryngealinlet. The outer cuff shape ensures that the blood flow to the laryngeal and perilaryngeal framework is maintained and helps the possibility to reduce neurovascular compression trauma to the nerves. The device has buccal cavity stabilizer which has propensity to adopt its shape to oropharyngeal curvatureof the patients. Itis anatomically widened and concaved to eliminate thepotential for rotation, thereby reducingthe riskof malposition. This buccalcavity stabilizer housesairway tubingand separate gastric channel. The tube section is firmer than the soft bowlof the gastric channel. The firmness of tube section and its naturaloropharyngeal curvature allows the device to be inserted by grasping the proximalend of it against the hard palate into the pharynx without inserting the fingers into the mouth ofthe patients 1 .The smooth contiguous surfaceof the device from the tip of the bowl to the proximal end of the tube, allows the device to easily slide posteriorly along the hard palate, pharynx and hypopharynx. The device has integral bite block which is marked with a horizontally placed blackline, which acts as a guide to depth of insertion. The device also has a channel for gastric tube drain (except size 1), which runs throughthe device from its proximalopening at the slide of flat connector wing to the distaltip of thenon inflatable mask. Thegastric channelallows suction, detection of leakand passage of gastric tube. The maximum size of gastric tube which can be passed through different sizes is given in Table 1.The device also has an epiglottic blocker ( Fig.1) which prevents downfoldingoftheepiglottis andobstruction ofthe distal opening airway.
The size of I-gel is selected accordingto patient's body weight (Table 1). I-gel can be used for intubation

Methods
Fifty consecutive patients of either sex belonging to ASA physical status I -III were recruited for this study after approvalfrom institutionalethical committee with informed written consent. The patients with anticipateddifficult airway,pregnancy, obesityand those who required surgery in positions other than supine or lithotomy positionor requiredIPPV wereexcluded from the study.
All the patients received oral alprazolam and ranitidine inthe nightbefore surgeryand in the morning on the day of surgery. In the operation room an IV line was secured and monitorswere appliedwhich included ECG, pulseoximetry and capnography. Induction of anaesthesia in each case was done in supine position with the head on the standard pillow (7-10 cm). Patientswere given,fentanyl(1-1.5µg.kg -1 )and midazolam (0.02 mg.kg -1 body weight). After preoxygenation for 3 minutes , each patient received induction dose of propofol (2-2.5 mg.kg -1 ) over 30-40seconds with end point of induction being loss of eyelash reflex .Face mask ventilation was done with 33% O 2 in N 2 O and 1-2% of halothane until optimalconditions for I-gel insertion were attained (Jaw relaxation, no movement). Additional increments of propofolwere given as and when required until level of anaesthesia adequate for insertion of devicewas achieved. The insertion of I-gel wasdone accordingto manufacturer's instruction. The front, back and sides of the cuff were lubricated with water based jelly. The patient's head was placed in 'sniffing the morning air'position. The lubricated device was grasped alongthe integralbite block and was introduced into the mouth in the direction towards the hard palateand wasglided downwards and backwards alongthe hard palate untildefinite resistance was felt. The device was connected to breathing circuit and patient ventilated manually.An effective airway was confirmed by bilateralsymmetricalchestmovement, square waveform on capnograph and normal SpO 2 (>95%). The device was secured with adhesive tape.
If the airway wasnot effective, manipulations were  Table 1. done in the form of increasing the depth of insertion, giving jaw thrust or chin lift or changingsize of the device. If it was not possible to maintain an effective airway after 3 insertion attempts; the device was taken as failure and alternative technique (proseal-LMA or ETT) was used.
Ventilation of patient was manually assisted until the spontaneousbreathingresumed.Oropharyngealseal pressure wasdetermined byclosingtheexpiratory valve at a fixed gas flow of 5 L/min(Magill circuit) and recording the airway pressure at which the gas leaked into the mouth 2 .
Towards the end of the procedure but before discontinuing anaesthetic, the stability of the device was evaluated in differenthead/neckpositions.This involved placing the head and neckin four sequential positionshead on standard pillow, head rotated to side, chin lift, and head without standard pillow and recording five consecutive tidalvolumes under a constant levelof anesthesia depth 3 . At the end of procedure all the patients breathed 100% O 2 during emergence from anaesthesia. The device was removed when patient was able to open the mouth on command. The patient was inspected about any injury to the lips, teeth or tongue and device was inspected for any blood stain.

Results
The patient characteristics and type of surgeries are shown in Table 2.
Size 3 was used in 84 % of cases and size 4 was used in 16 %.In 2 patients the device was replaced with larger size to achieve better seal.
The device was easy to insert and remove. The success rate at first attempt was 45/50 (90%) with a median insertion time of 11 seconds (range 8-45 seconds). Five patients needed 2 nd attempt while none needed 3 rd attempt or had failure of insertion.The most commonmanipulations toachieve effectiveairway was increasingthe depth of insertion of I-gel(8%). Airway manipulations in the form of chin liftor jaw thrust were needed in 2% patients (Table 3). In two cases the device was replaced with a larger size to achieve better seal. Gastric tube placement was done only in 50% of thepatients and it waseasy and successfulineach case. No patient had gastric distention. There was no clinical evidence of aspiration in any patient.
No significant adverse event was noted in any patient. The incidence of adverse events during perioperative period was low (Table 4). Two patients achieve effective airway. The additionaladvantages are high seal pressure and stability of device despite changes in position of head and neck. All the anaesthetists stated that the placement of I-gel was certainly easier than any other currently available supraglottic device. This greater stability is primarily relatedto theanatomical design of thenon-inflatable cuff. The ridge at the proximalend of maskcatches the base of tongue thus preventsthe device from movingand so contributes to the positionalstability of thedevice after placement 4 . Since no cuff inflation is needed in this device, there is shorter time to achieve effective airway.
Asupraglottic airwaydevice withoutinflatable cuff has some potentialadvantages including easier insertion and minimal risk of tissue compression 5-7 whereas supraglottic device with inflatable cuff can absorb anesthetic gases leadingto increased mucosalpressure 8 .Igelmay find a place during CPR due to high success rate at first attempt alongwith quickinsertion time 9,10 . Also, easy ventilation of chest without air leak during chest compression may haveadditional advantage.
Intra operative problems like arterialdesaturation and haemodynamic changes were not seen in any patient probably due to shorter time for successful placement of the device.
As this is a new device very little published data is available regardingits use during anaesthesia. Most of the studies are manikin or cadaverstudies andthese are mainly aimed to evaluatethe easeof success of insertion by non-anaesthetist. I-gelhas been found to have easiest insertionin various types of manikins 11 .Levitan and Kinkle 4 studied thepositioning andmechanics ofthis device in 65 non embalmed cadavers with endoscopies and neckdissections. Aglottic openingscore (POGO) of >50% was obtained in all 65 cases. In each of the neckdissections the bowl of device wasfound covering the laryngeal inlet. In a study on cadavers, I-Gel was consistentlypositioned over laryngealinletas confirmed by endoscopy, radiography and dissection 4 . It was also usedto facilitate endotracheal intubation 12 .  (4%) had suboptimal oxygenation (SpO 2 <95%) for which airway manipulationin theform of increasing the depth of insertion was done which rectified the problem. None of the patient sufferedhypoxia (SpO 2 <90%). During emergence 2 patients (4%) had cough and 2 (4%) patient complained of sore throat in the postoperative period which subsided within24 hrs. None of the patient complained of dysphonia or dysphagia

Discussion
Theresults ofthe present clinical trialhave shown many advantages of I-gel. These include high success rate at first attempt, easy insertion and shorter time to We concluded that I-gel is a simple, excellent and easy to use supraglottic airway device. It is easy to insert withoutneed ofmany manipulationswith maintenance of airway in a short time. The device is very effective and useful for adult patients requiringsurgical procedures of 30-60minutes duration while breathing spontaneously. We strongly believe that I-gelmay become very popular due to its superior qualities of speedy yet successfulinsertion and ventilation. However more studies with large number of patients are required to further validate our results before recommending its widespread use. Our study was conducted on spontaneously breathinganaesthetized patients, we did not studied it for controlled ventilation.